In the past, and especially in recent years, the laboratory techniques of competitive binding assay and competitive radioassay have become increasingly valuable tools for analysis of biological materials. These techniques have become particularly important in medical research for determining the presence or absence of particular biological substances which are indicative of particular medical conditions in a subject. While the term "radioimmunoassay" has frequently been used to describe all forms of competitive radioassay and competitive binding assay, many other forms of these more general terms besides radioimmunoassay are common laboratory procedures. Appropriate terms include radioenzymatic assay, radiostereoassay, saturation analysis, displacement analysis, and competitive protein binding.
Whatever the particular technique, the procedure usually involves the tedious preparation of a great multiplicity of samples from a smaller number of specimens. Dilution of the specimen material and replication of the samples produced is typical in these laboratory techniques. The samples must be handled a number of times to achieve dilution and replication as well as intermediate incubation and subsequent centrifugation. Because of the great number of discrete chemical mixtures involved, the processing of a single batch of specimens requires a considerable amount of time by laboratory personnel. Furthermore, because of the tedious nature of the manual steps involved, mistakes in the manual manipulations of specimens and samples are far too frequent. For these reasons, there has existed a chronic need for a device to process a batch of specimen materials and yield as a product samples ready for analysis along with sample standards and batch controls, with only a periodic requirement for manual attention.
At present, no appropriate device exists. The machines most useful in the preparation of samples for competitive binding assay have eliminated but a minor portion of the manual attention involved. For example, a laboratory device exists which will withdraw specimen material from a test tube in a first column of tubes, and deposit the specimen material in a mixture with a buffer diluent in an adjacent test tube in a second column of tubes. Processing of specimens can occur only on a one-to-one basis. That is, a single tube in the first, or specimen column can yield but a single sample in the second, or sample column. In competitive binding assay, however, it is frequently desirable to have a plurality of dilutions of each specimen and replicate samples of each dilution. Where two dilutions in duplicate are required from each specimen, four samples must be produced from each specimen processed. Where the specimen material, and two dilutions thereof are each required in triplicate, nine samples must be produced from each specimen. It can be seen that because of limitations imposed by the one-to-one production of samples from specimens with the above sample preparation unit, a single batch of specimen materials must be processed a plurality of times in order to produce the required number of samples. Also, the existing device has no provision for the creation of sample standards, or batch controls, which are essential in all forms of competitive binding assay. Furthermore, the specimen columns and the sample columns of test tubes are provided in the form of engagable test tube holders, which are engaged only during sample preparation and which must thereafter be disengaged so that the specimen tubes are again available for the preparation of additional samples in the recurring sample preparation steps which must be applied to each specimen. Also, the volume of reagent and buffer to be added must be manually adjusted. This adjustment must typically be made at the end of one cycle in the processing of a single specimen batch and before a subsequent cycle is initiated. The test tubes are thereby grouped in only a single column, usually from ten to fourteen in number, and the samples produced from a single specimen are not grouped together. This separation of samples from a common specimen, and the large number of test tube groupings involved, aggravate an existing problem of difficulty in sample identification.